feat(Show Originals): Allow filtering blog search/tagged/filtered-by-type

[marcustyphoon]

Description

*staring off into the middle distance and taking a shaking sip from a proffered thermos, mylar blanket crinking* "there has got to be a better way. right. I mean. surely."

somewhat related to, and probably about as niche as, #1378. (by which I mean I want them.)

Testing steps

open a blog in peepr and turn show originals on on said blog.

confirm that show originals shows a default-off but functional control element on that blog when:

• filtering by post type (nothing in search bar)
• searching for something
• searching for something and [filtering by post type or not, filtering by original posts or not, and viewing top posts first or not]; all 8 combinations should work
• viewing posts with a certain tag
• viewing posts with a certain tag and filtering by post type

clear the search and confirm that show originals goes back to being on, as it remembered your preference for viewing blogs in peepr with no filter.

[marcustyphoon]

Related: #1985.